Controlled Conversion of Proteins into High-Molecular-Weight Peptides without Additives with High-Temperature Water and Fast Heating Rates

Reaction of bovine serum albumin (BSA) protein in high-temperature (200−260 °C) water (HTW) with fast heating rates (ca. 135−180 K·s^–1) without acid or base additives gives high-molecular-weight (1500–8300 Da) peptides with minimal formation of amino acids and ammonia. The decrease in the number-average molecular weight of peptides after HTW treatment of BSA could be described by a kinetic model based on random scission mechanism of the polymer chain. Reaction of BSA in HTW under identical conditions with slow heating rates (ca. 0.25 K·s^–1) gives peptides of low molecular weight with formation of amino acids and ammonia for which the kinetics could not be described by a random scission mechanism. The activation energy determined for the conversion of BSA into high-molecular-weight peptides with fast heating rates in high-temperature water was 16.4 kJ·mol^–1. Reaction of proteins in high-temperature water with fast heating rates inhibits initial aggregation that occurs during slow heating rates and allows controlled conversion of the denatured polymer chain into high-molecular-weight peptides

Measurement of High-Pressure Densities and Atmospheric Viscosities of Ionic Liquids: 1‑Hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide and 1‑Hexyl-3-methylimidazolium Chloride

Atmospheric densities and viscosities of ionic liquids, 1-hexyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide ([C₆C₁Im]­[Tf₂N]) and 1-hexyl-3-methylimidazolium chloride ([C₆C₁Im]­[Cl]), were measured with a Stabinger viscometer at temperatures from (293 to 373) K. High-pressure densities (<i>p</i> ≤ 200 MPa) for [C₆C₁Im]­[Tf₂N] and [C₆C₁Im]­[Cl] were measured with a bellows type apparatus at temperatures from (312 to 452) K. Samples were analyzed for the water and 1-methylimidazole content before and after the measurements. For [C₆C₁Im]­[Tf₂N], combined expanded uncertainties were estimated to be (1.0 and 1.8) kg·m^–3 for atmospheric and high-pressure density, respectively, and 0.85 % for viscosity. For [C₆C₁Im]­[Cl], combined expanded uncertainties were estimated to be (1.1 and 2.5) kg·m^–3 for atmospheric and high-pressure density, respectively, and 1.59 % for viscosity. The measured densities and viscosities of [C₆C₁Im]­[Tf₂N] in this work agreed with some of the available literature values within their experimental uncertainties. The effect of colored impurities and the source of sample on densities and viscosities of [C₆C₁Im]­[Cl] were determined to be less than the experimental uncertainties. The [C₆C₁Im]­[Tf₂N] did not decompose over the full temperature range during the measurements, while [C₆C₁Im]­[Cl] decomposed at temperatures greater than 392 K

Winterization of Vegetable Oil Blends for Biodiesel Fuels and Correlation Based on Initial Saturated Fatty Acid Constituents

Winterization is a simple method to remove saturated fatty acid contents in biodiesel fuels for improving their cold flow properties. In this work, biodiesel fuels with different initial long-chain (C16 and above) saturated fatty acid constituents (<i>S</i>_i) were prepared from blends of palm, canola, and corn oils. The prepared biodiesels were treated at various winterization temperatures (<i>T</i>_w) to investigate the effect of <i>T</i>_w and <i>S</i>_i on the final saturated fatty acid constituents (<i>S</i>_w) of the winterized biodiesel fuel. Optical microscopy showed that ball-like crystals formed with fluid regions at moderate cooling rates (−6 °C/h) could allow solid–liquid separation by filtration. A saturated fatty acid reduction ratio, <i>R</i>_s, defined as (<i>S</i>_i – <i>S</i>_w)/<i>S</i>_i × 100, was used with the experimental results on large samples (ca. 600 mL) to develop a correlation for winterization temperature as <i>T</i>_w (°C) = 0.659 <i>S</i>_i (wt%) – 0.104 <i>R</i>_s (wt%) – 10.197. The correlation can provide estimation of the required winterization temperature for reducing a specified ratio of fatty acids in a biodiesel fuel that mainly contains long-chain fatty acids from the initial saturated fatty acid constituents. When used with literature relationships for cold filter plugging point (CFPP) and <i>S</i>_w, estimation of the CFPP of winterized biodiesel fuels is possible without requiring actual winterization treatment